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Hi ~
I test my kernel on real machine and find an interesting thing. my kernel detected the following memory region:
...
base len usage
0x3f6d0000 0xe000 occupied
0x3f6de000 0x12000 occupied
0x3f6f0000 0x1000 occupied
....

a small memory region located at about 1G address.
i can't get useful information by google, if no one knows,ii think i should check my code.

believe me, i aligned that three lines of screen message very carefully, but the space characters seems deleted by osdev when i post the thread.

Probably something related to ACPI.

(Use code-tags to keep alignment using spaces.)

Use the (code)(/code) tags. It then uses a fixed font to display the code.

These will most likely be memory mapped devices. If you enumerate your PCI(e) bus, displaying all of the BARs associated with those devices, you will most likely have one to three devices showing these values in their BARs, (Base Address Registers).

Ben

BenLunt wrote:These will most likely be memory mapped devices. If you enumerate your PCI(e) bus, displaying all of the BARs associated with those devices, you will most likely have one to three devices showing these values in their BARs, (Base Address Registers).

The ACPI specification explicitly forbids the firmware from indicating PCI devices in the memory map. It's either memory reserved for ACPI, or some other MMIO hardware.

Those addresses (around 1G) are pretty low for MMIO hardware, so it's probably RAM being used by ACPI.

If you call INT 0x15, EAX = 0xE820 in your boot loader, you can get a little more information about why the memory area is reserved. Most Linux distros will let you browse through these tables at boot time as well.

Or, you can just run Windows and look at the Device Manager. It will tell you what device is using what memory address.